Questions! So many questions!

Actually, just two: could I be pregnant? If not, WHAT IS HAPPENING?
I had unprotected sex about 5 weeks ago, in the middle of my fertility window. Since then, I get nauseous easier, I thought something was wrong with my blood pressure because I kept almost fainting when I got up/ sat up, I've had pains twice that feel like a lightning bolt going up my vagina towards my cervix, and now light cramping, no bleeding, with bloating. HOWEVER, I don't have sore breasts or any areola change, I had a period between the sex and now, and a test I just took at 1 am with very little urine said "Not Pregnant"
Could I just have low pregnancy hormone levels? Is it mid cycle pain, and something else explains the other symptoms? What's the other thing?? 
Please help!